The power density, reliability, and cost of a dynamoelectric machine are directly related to the physical size and complexity of the machine. Accordingly, manufacturers of dynamoelectric machines continually strive to reduce the complexity and physical size of their machines in an attempt to improve power density, provide enhanced reliability, and reduce cost.
Design improvements allowing reductions in the axial length and the complexity of rotors used in dynamoelectric machines are of particular interest in this regard. During operation, the rotor and associated support structures are subjected to high centrifugal forces and bending movements caused by rotation of the rotor and high internal magnetic fluxes incident with operation of the dynamoelectric machine. This is particularly true in dynamoelectric machines designed for use in aircraft which typically operate at high rotational speeds and utilize very high magnetic flux densities in order to achieve maximum performance with a machine of minimum size and weight.
As the axial length of the rotor is decreased, problems associated with critical speed and bending of the rotor are also diminished. This in turn allows reduction in the size of structural elements comprising the rotor and corresponding reduction in the size of structures supporting the rotor. It will be appreciated, therefore, that, as a result of reductions in the size of structural elements comprising and associated with the rotor, reduction in the axial length of the rotor will allow an overall reduction in the size of the dynamoelectric machine greater than would have been derived solely from the reduction in axial length of the rotor alone.
As complexity of the rotor is decreased, size and cost of the rotor also decrease. As a result, rotor designs comprised of a minimal number of simple parts are highly desirable.
Through the years, designers and manufacturers of dynamoelectric machines have devoted considerable effort toward advancing the state of the art in the design and manufacture of dynamoelectric machines in general, and more specifically toward reduction in the axial length and complexity of the rotors utilized in these machines. Typical of these past efforts are U.S. Pat. No. 3,292,025 to Victor; U.S. Pat. No. 4,217,515 to Long et al; U.S. Pat. No. 4,598,223 to Glennon et al; U.S. Pat. No. 4,603,274 to Mosher.
U.S. Pat. No. 3,292,025 to Victor describes a rotor end winding having a special conductor configuration in an end turn region of a rotor in conjunction with a special coil-to-coil connector which allows a radial transition to be made between coils in the end turn region, thereby removing the necessity for an overlapping or extra conductor layer.
The Victor patent is directed to connections between coils in a rotor having a winding made up of multiple separate coils, whereas the present invention, to be described hereinafter, utilizes a rotor having a winding formed as a single continuous coil, and does not, therefore, require coil-to-coil connectors. In addition, the present invention addresses configuration and termination of the exciter lead portions of the winding, whereas Victor addresses only coil-to-coil connections and does not address the exciter lead portions of the windings.
And finally, Victor states that an object of his invention is to provide an arrangement "which does not employ extra turns or overlapping turns at the end of the rotor", thereby specifically teaching away from the present invention which is directed in part to defining a manner in which the exciter lead portion of the winding can be conveniently crossed underneath the winding at the core ends.
U.S. Pat. No. 4,217,515 to Long et al describes means for embedding end turns of field windings for a rotor in the rotor and restraining the field windings in the rotor by use of wedge means. The rotor of the present invention, to be described hereinafter, utilizes a construction radically different from Long, particularly with regard to placement and support of end turns and the method utilized to restrain the windings.
U.S. Pat. No. 4,598,223 to Glennon et al, assigned to the assignee of the present invention, describes a unique construction for the end turns of stator windings in dynamoelectric machines and is directed to an improved stator end turn construction which provides capability for enhanced cooling and/or a reduction in axial length of the machine. The Glennon patent is directed specifically to stator end turns and does not address the rotor or end turns of windings in a rotor.
U.S. Pat. No. 4,603,274 to Mosher, also assigned to the assignee of the present invention, describes a structure for facilitating precision machine winding of a rotor for a high speed machine and a method of producing a rotor utilizing the structure as defined. Mosher utilizes an insulator having radially spaced rows of notches for guiding turns of a winding to predetermined locations in a precision wound rotor. Wedges are attached following winding to prevent distortion of the winding due to centrifugal forces incident with rotation of the rotor.
Mosher is of special interest because both Mosher and the present invention incorporate structures made from insulative material at each core end, these structures being specifically denoted as an "insulator", according to Mosher, and as the "winding end support" in the present invention. However, the configuration and functions performed by the winding end support of the present invention, described hereinafter, are significantly different from the configuration and function of the insulator of Mosher.
In light of the following description of the present invention, it will be readily appreciated that the present invention is clearly patentably distinct from, and constitutes significant improvement over, prior dynamoelectric machines.